Search

This study investigates the representation of the temporal progression of events by means of the causal change in a patient. Subjects were asked to verify the relationship between adjectives denoting a source and resulting feature of a patient. The features were presented either chronologically or inversely to a primed event context given by a verb (to cut: long-short vs. short-long). Effects on response time and on eye movement data show that the relationship between features presented chronologically is verified more easily than that between features presented inversely. Post hoc, however, we found that the effects of temporal order occurred only when subjects read the features more than once. Then, the relationship between the features is matched with the causal change implied by the event context (contextual strategy). When subjects read the features only once, subjects respond to the relationship between the features without taking into account the event context.

Scripts store the temporal order of component events of everyday activities as well as the temporal position of the events within the activity (early or late). When confronted with an activity, predictions are generated about how the component events will unfold. Thereby, an error-detection mechanism continuously monitors whether they unfold as anticipated or not in order to reveal errors in the unfolding activity. We investigated whether the temporal position "early" or "late" influenced the detection of errors using the pupillary response as an index of cognitive resource consumption. An event triplet consisting of three events was presented in a chronological or non-chronological temporal order. Crucially, the triplet focused either on the beginning (temporal position "early") or the end (temporal position "late") of an activity. We assumed that these position codes would be used to facilitate error detection when a non-chronological event was presented. Results showed that errors in the temporal order were detected more successfully in early than in late triplets. Results further suggest that strong predictions are formed about how an activity begins. Violations of this prediction must be overcome by zooming into the representation and allocating attention to the temporal position that consumes cognitive resources. Only after zooming in has taken place successfully may the position codes be used to anticipate temporal violations in unfolding event sequences.

Early visual areas (V1, V2, V3/VP, V4v) contain representations of the contralateral hemifield within each hemisphere. Little is known about the role of the visual hemifields along the visuo-spatial attention processing hierarchy. It is hypothesized that attentional information processing is more efficient across the hemifields (known as bilateral field advantage) and that the integration of information is greater within one hemifield as compared with across the hemifields. Using functional magnetic resonance imaging we examined the effect of distance and hemifield on parallel attentional processing in the early visual areas (V1-V4v) at individually mapped retinotopic locations aligned adjacently or separately within or across the hemifields. We found that the bilateral field advantage in parallel attentional processing over separated attended locations can be assigned, at least partly, to differences in distractor position integration in early visual areas. These results provide evidence for a greater integration of locations between two attended locations within one hemifield than across both hemifields. This nicely correlates with behavioral findings of a bilateral field advantage in parallel attentional processing (when distractors in between cannot be excluded) and a unilateral field advantage if attention has to be shifted across separated locations (when locations in between were integrated).

In the present study, we examined the hypothesis of task-specific access to mental objects from verbal working memory. It is currently assumed that a mental object is brought into the focus of attention in working memory by a process of object selection, which provides this object for any upcoming mental operation (Oberauer, 2002). We argue that this view must be extended, since the selection of information for processing is always guided by current intentions and task goals. In our experiments, it was required that two kinds of comparison tasks be executed on digits selected from a set of three digits held in working memory. The tasks differed in regard to the object features the comparison was based on. Access to a new mental object (object switch) took consistently longer on the semantic comparison task than on the recognition task. This difference is not attributable to object selection difficulty and cannot be fully accounted for by task difficulty or differences in rehearsal processes. The results support our assumptions that (1) mental objects are selected for a given specific task and, so, are accessed with their specific task-relevant object features; (2) verbal mental objects outside the focus of attention are usually not maintained at a full feature level but are refreshed phonologically by subvocal rehearsal; and (3) if more than phonological information is required, access to mental objects involves feature retrieval processes in addition to object selection.

Event-related potentials were measured to investigate the role of visual spatial attention mechanisms in conflict processing. We suggested that a more difficult target selection leads to stronger attentional top-down control, thereby reducing the effects of arising conflicts. This hypothesis was tested by varying the selection difficulty in a location negative priming (NP) paradigm. The difficult task resulted in prolonged responses as compared to the easy task. A behavioral NP effect was only evident in the easy task. Psychophysiologically the easy task was associated with reduced parietal N1, enhanced frontocentral N2 and N2pc components and a prolonged P3 latency for the conflict as compared to the control condition. The N2pc effect was also obvious in the difficult task. Additionally frontocentral N2 amplitudes increased and latencies of N2pc and P3 were delayed compared to the easy task. The differences at frontocentral and parietal electrodes are consistent with previous studies ascribing activity in the prefrontal and parietal cortex as the source of top-down attentional control. Thus, we propose that stronger cognitive control is involved in the difficult task, resulting in a reduced behavioral NP conflict.

Scripts are mental representations of activities in memory and are thought to be organized dimensionally in a temporal dimension. We investigated the cognitive strategies during the processing of temporal order of an event sequence to gain insight into the organization of scripts. Subjects were presented with triplets of script events (A - B - C). Fifty percent of the items included sequence violations at different positions within the triplet (late: A - C - B, or early: C - A - B). Reaction times indicate that subjects use an economical strategy by comparing the relative temporal positions of event pairs (e.g., A vs. B and if necessary B vs. C) and only attend to information that is necessary. Pupil data and error rates indicate that the temporal information of the complete sequence affects the decision process even if the first event pair indicates that temporal order has been violated. Results are seen as evidence of a dimensional structure of scripts.

Selective attention enables us to respond to objects and events that are relevant to our goals for adaptive interactions with the environment. Despite evidence from research addressing the selection of a target location, little is known about the neural mechanisms of attentional selection in situations in which the selection is biased in favor of the information in the irrelevant location. In this study, we combined event-related fMRI and a location-based negative priming paradigm with a prime–probe-trial design to investigate the neural mechanisms of spatial attentional selection. Participants were instructed to respond to the location of a pre-specified target while ignoring a distractor at an irrelevant location. The goal of this study was twofold. First, we identified brain regions that are linked to conflict resolution situations, in which the selection bias puts the irrelevant information in the probe trial on a selection advantage over the target. Second, we determined the mechanism of conflict resolution when the encoding conditions of stimuli are manipulated by presenting stimuli either abruptly (onset) or masked (no-onset). The results showed that the bottom-up-induced competition among stimuli in the target selection is stronger for onset than no-onset stimuli. The superior parietal lobule was sensitive to those changes in bottom-up-induced competition. Furthermore, the dorsolateral prefrontal cortex and inferior parietal lobe were activated to resolve the additional processing effort necessary to select the negatively biased target. In conclusion, the present study identified dissociable neural components needed to resolve the negative selection bias, which attentional modulation can be addressed in future studies by examining changes in the functional connectivity.

We quantified the interference of distracter stimuli on sustained visuo-spatial attention as a function of the distribution of attended positions in the visual fields (bilateral/unilateral, left/right, upper/lower), distracter positions (peripheral, between attended positions, between fixation and attended positions) and task difficulty. Compared to distinct distracter positions, bilateral field and lower field presentation had much stronger influence on the performance. Additionally, interactive effects between task difficulty and distracter position were found. This result was at variance with the previous models of visuo-spatial attention, which attached much more importance to the role of distracter positions compared to visual field effects. In directly comparing the impact of the abovementioned factors, the converse finding is evident-visual field effects, in particular bilateral presentations have a much stronger importance. Moreover, metaphoric concepts of attention like the "zoom lens" are not compatible with these results. The findings are discussed in the light of alternative models of sustained visuo-spatial attention. The visual system architecture and top-down mechanisms are considered.

Current fMRI retinotopic mapping procedures often use checkerboard stimuli consisting of expanding rings and rotating wedges to measure the topography within human visual areas. Efficient procedures are well described in the literature. For many experimental paradigms, e.g., visuo-spatial attention paradigms, the identification of task-relevant positions is the only mandatory prerequisite. To define these specific "regions-of-interest" (ROIs), spatially defined localizers are used. A precise evaluation of localizer techniques in regard to efficient scanning time, optimal BOLD (blood oxygenic level dependent) response, as well as quantification of the resulting ROIs within each visual area (size, overlap, surround effects) has not been studied to date. Here, we suggest a mapping procedure designed to quantify spatial and functional properties of single positions at close proximity in multiple human visual areas. During a passive viewing task, various stimuli (e.g., checkerboards or colored objects) subtending 1.4 degrees of visual angle were presented at one out of four positions in a randomized block design. We measured the degree of overlap between positions at different hierarchical levels of the visual system (V1-V4v) and quantified modulatory effects on a specific position by stimulation at neighboring (1.7 degrees spacing) or distant positions (5.1 degrees or 8.5 degrees spacing). Within each visual area, "mexican-hat" distributions of local signal intensity changes, which describe a particular combination of facilitatory and suppressive effects, were found. Cubic fitting revealed the most localized tuning effect in V1, which gradually decreased throughout the higher visual areas. Colored objects were most efficient in localizing circumscribed retinotopic positions in both early and higher areas.

In a location-based negative priming paradigm, the possibility of a disengagement option of the underlying inhibitory mechanism was tested. Whereas in previous studies disengagement was observed when providing utility information about the probe trial structure, in the present study the allocation of visual attention to the stimuli was manipulated. In the first step an automatic deployment of visual attention was implemented by presenting all stimuli as abrupt onsets (Experiment 1), which demonstrated commonly observed negative priming effects. In further conditions of non-automatic allocation of visual attention in which target and distractor were presented as no-onset stimuli, negative priming effects were eliminated (Experiments 2 and 3). The preferred interpretation is that in conditions of automatic control of attention, target and distractor compete for control of action. A non-automatic control of visual attention, on the other hand, leads to a top-down modulated selection, which results in prioritized target encoding and a loss of distractor impact on the selection process. Alternative accounts and the role of no-onset distractor processing were investigated in Experiment 4.

The present study explores the processing of temporal information in event knowledge by focusing on the transition from an earlier, source state to a later, goal state. Participants were presented with an event verb followed by antonymous adjectives or adverbs denoting an earlier state and a later state. The states were presented either chronologically (to cook: cold – hot) or inversely (to cook: hot – cold) with regard to the denoted event. Participants were asked to identify either the earlier or the later state. We found that later states are identified faster and more accurately than earlier states. Later states presented chronologically were identified even more quickly than later states presented inversely. We attribute our results to the fact that directedness towards the goal state is a general principle of cognition which plays a fundamental role in language and in simulation, whereby language processing provides faster and more direct access to goals even than simulation.

Event knowledge includes persons and objects and their roles in the event. This study investigated whether the progression of patients from a source to a resulting feature, such as the progression of hair that is cut from long to short, forms part of event representations. Subjects were presented with an event prime followed by two adjectives and asked to judge whether the adjectives were interrelated. Results showed that the semantic interrelation of two adjectives is recognized faster and more accurately when the adjectives denote source and resulting features of the patient of the primed event (“cutting”: long–short). Furthermore, we found that presenting an event-related adjective in combination with an unrelated adjective makes it more difficult to recognize that the two adjectives are not interrelated, but only when the event-related adjective denotes a source feature. We argue that an inference mechanism automatically completes the representation of the event. We conclude that source and resulting features are represented in a goal-directed and chronological way.

Coordination of mental procedures is considered in terms of control processes (Baddeley, 1989) in visual working memory and appears to be a separable aspect of the demand imposed by cascaded serial processes (Carlson & Lundy, 1992). The main task required subjects to indicate whether symbolically suggested rotations and reflections correctly describe the difference between matrix patterns of filled-in squares within a 3 x 3 grid or between line drawings. Experiments were carried out to show that coordination is a separable component in this transformation task. A marker for coordination is the difference between the time taken to execute two transformations as a whole and the sum of the component transformations in isolation. The separate coordination demand was found in an experiment with matrix patterns mentioned, in an experiment with letter-like line drawings, and also in an experiment that forced subjects to maintain whole-pattern representations. A last experiment checked whether coordination is carried out by an autonomous control unit. There was a self-paced control of serial presentation of transformation symbols instead of a simultaneous presentation of those symbols. This additional external triggering resulted in a substantial decrease in the demand for coordination. Coordination of mental procedures and temporary representations is a fundamental constraint on the use of working-memory processes.

Early visual areas (V1, V2, V3/VP, V4v) contain representations of the contralateral hemifield within each hemisphere. Little is known about the role of the visual hemifields along the visuo-spatial attention processing hierarchy. It is hypothesized that attentional information processing is more efficient across the hemifields (known as bilateral field advantage) and that the integration of information is greater within one hemifield as compared with across the hemifields. Using functional magnetic resonance imaging we examined the effect of distance and hemifield on parallel attentional processing in the early visual areas (V1-V4v) at individually mapped retinotopic locations aligned adjacently or separately within or across the hemifields. We found that the bilateral field advantage in parallel attentional processing over separated attended locations can be assigned, at least partly, to differences in distractor position integration in early visual areas. These results provide evidence for a greater integration of locations between two attended locations within one hemifield than across both hemifields. This nicely correlates with behavioral findings of a bilateral field advantage in parallel attentional processing (when distractors in between cannot be excluded) and a unilateral field advantage if attention has to be shifted across separated locations (when locations in between were integrated).

Sinnliche Empfindungen kommen zustande, indem ausere Reizmittel auf die empfindlichen Nervenapparate unseres Korpers einwirken, und diese in Erregungszustand versetzen. Die Art der Empfindungen ist verschieden, theils nach dem Sinnesorgan, welches in Anspruch genommen worden ist, theils nach der Art des einwirkenden Reizes. Jedes Sinnesorgan vermittelt eigenthumliche Empfindungen, welche durch kein anderes erregt werden konnen, das Auge Lichtempfindungen, das Ohr Schallempfindungen, die Haut Tastempfindungen. Selbst wenn dieselben Sonnenstrahlen, welche dem Auge die Empfindung des Lichts erregen, die Haut treffen und deren Nerven erregen, so werden sie hier doch als Warme, nicht als Licht empfunden, und ebenso konnen die Erschutterungen elastischer Korper, welche das Ohr hort, von der Haut empfunden werden, aber nicht als Schall, sondern als Schwirren. Schallempfindung ist also die dem Ohr eigenthumliche Reaktionsweise gegen ausere Reizmittel, sie kann in keinem anderen Organ des Korpers hervorgebracht werden, und unterscheidet sich durchaus von allen Empfindungen aller ubrigen Sinne.

Der Duft ist ein machtiger Zauberer, der uns uber Tausende Meilen hinwegtragt, uber all die Jahre, die wir gelebt haben. Der Duft der Fruchte tragt mich in meine Heimat im Suden, erinnert mich an mein kindliches Herumtollen zwischen Pfirsichbaumen. Andere Dufte, spontan und fluchtig, offnen mein Herz vor Freude oder verkrampfen es in schmerzlicher Erinnerung. Allein der Gedanke an Dufte weckt in mir liebe Erinnerungen an langst vergangene Sommertage und reifende Weizenfelder in der Ferne.

Personen konnen eine Menge verschiedener Dinge sehen. Sie konnen Baume, Sterne, Planeten, Berge, Flusse, Stoffe, Tiger, Menschen, Dampf, Regen, Schnee, Gas Flammen … Bilder, Zeichen, Filme, Handlungen sehen. Sie konnen Eigenschaften von Dingen wie die Farbe, Textur, Orientierung, Form, Kontur, Ort, Bewegung von Objekten sehen. Sie konnen Fakten sehen, beispielsweise den Fakt, dass ein Objekt eine Menge visueller Merkmale enthalt oder in einer visuellen Beziehung zu einem anderen Objekt steht. Sehen, visuelle Erfahrung oder visuelle Wahrnehmung ist sowohl eine besondere Art menschlicher Erfahrung als auch eine grundlegende Quelle menschlichen Wissens der Welt. Weiterhin interagiert die visuelle Wahrnehmung in vielfaltiger Weise mit dem Denken, Gedachtnis und dem Rest der Kognition.

Regen peitscht auf die Windschutzscheibe, die Kreuzung verschwimmt zwischen den Scheibenwischern. Im Radio wird vor einem Orkan gewarnt. Da klingelt plotzlich das Telefon. Oder ist es das Signal, dass das Ol alle ist? Muss ich nach rechts oder links? Was sagt das Navigationssystem? Es ist das Telefon, ich kann doch jetzt nicht telefonieren!

Die Bedeutung der Selektionsfunktion der Aufmerksamkeit wird deutlich, wenn man sich vergegenwartigt, dass zu einem gegebenen Zeitpunkt eine grose Menge von auditiven, visuellen, taktilen etc. Reizen auf unsere verschiedenen Sinnesorgane einwirkt und sensorische Rezeptionsprozesse in Gang setzt. Allerdings wird uns nur ein kleiner Ausschnitt dieser Informationsmenge bewusst bzw. nur ein kleiner Ausschnitt aus dieser Menge determiniert unsere fortlaufende Interaktion mit der Umwelt. Das bedeutet, dass aus der Gesamtmenge der eingehenden sowie der im Gedachtnis gespeicherten Information immer wieder die relevante Teilmenge ausgewahlt werden muss, um effizientes und storungsfreies Handeln zu ermoglichen.

Nach einer Kohlenmonoxidvergiftung und zeitweiliger Blindheit erholte sich die visuelle Wahrnehmung des Patienten S. (Benson & Greenberg, 1969) weitgehend. Allerdings ein Defizit verblieb: Er konnte keine visuell dargebotenen Objekte benennen. Dagegen hatte er keine Schwierigkeiten bei der Benennung von Objekten, wenn er sie ertasten konnte. Er hatte noch ein relativ intaktes Auflosungsvermogen. Ebenso konnte er Objekte nach Farbe, Helligkeit und Grose vergleichen. Entsprechende Tests belegten, dass er ein normales Sehfeld hatte. Das zeitliche Auflosungsvermogen des visuellen Systems war auch im Normbereich. Weitere Tests zeigten allerdings ein Defizit in der Unterscheidung visueller Formen. Neben seinem Defizit in der Objekterkennung war er auch in der Erkennung von Gesichtern beeintrachtigt. Infolge der Schwierigkeiten in der Formwahrnehmung konnte er auch nur noch schlecht lesen.

Als ich gegen Abend in eine Wirtshaus eintrat und ein wohlgewachsenes Madchen mit blendenweisem Gesicht, schwarzen Haaren und einem scharlachroten Mieder zu mir ins Zimmer trat, blickte ich sie, die in einiger Entfernung vor mir stand, in der Halbdammerung scharf an. Indem sie sich nun darauf hinwegbewegte, sah ich auf der mir entgegenstehenden weisen Wand ein schwarzes Gesicht, mit einem hellen Schein umgeben, und die ubrige Bekleidung der vollig deutlichen Figur erschien von einem schonen Meergrun.

Wenn im Zuge der Informationsaufnahme sensorische Stimuli fur die weitere Verarbeitung selektiert wurden, erfolgt darauf haufig ein extern beobachtbares Verhalten, das zur Erreichung von bestimmten Zielen notig ist. So nimmt man den Stimulus eines roten Ampellichts nicht »nur« einfach wahr, um ihn zu sehen, sondern man fuhrt darauf eine Handlung aus; z. B. reagiert man darauf durch Betatigen des Bremspedals eines Autos. Im Zusammenhang mit der Ausfuhrung derartiger zielgerichteter Handlungen werden besondere Gesetzmasigkeiten der Aufmerksamkeit deutlich. Diese konnen gut in Situationen erforscht werden, in denen die Handlungsausfuhrung erhohte Anforderungen an die Verteilung der Aufmerksamkeit stellt.

Beim Ergreifen eines Gegenstandes melden spezielle Rezeptoren in Gelenken und Muskeln die Stellung von Armen, Beinen und Korper an das Gehirn. Die Tastrezeptoren der Haut vermitteln die Wahrnehmung der aufgewendeten Kraft und die Wirkungen des Gewichts des zu greifenden Gegenstandes. Schlieslich muss auch der Druck der Fuse zur Erhaltung des Gleichgewichts kontrolliert werden. All dies gelang Ian Waterman nicht mehr. Er hatte durch eine virale Infektion seine gesamte Korperwahrnehmung verloren. In einem aufwendigen Training gelang es ihm, uber den intakten visuellen Sinn seine Korperbewegungen wieder zu kontrollieren. Allerdings musste er fur diese Kontrolle die einzelnen Gliedmasen standig im Blick behalten. Er kompensierte den Verlust der Korperwahrnehmung durch die intakte visuelle Wahrnehmung. Der Sehsinn ubernahm die Rolle eines ausgefallenen Sinns (Cole, 1995).

Was ist nun unter allem, was wir wissen und was wir uns gegenseitig mitteilen konnen, das Allersicherste, das, was nicht dem geringsten Zweifel unterliegt? Darauf gibt es nur eine Antwort; es ist das, was wir selbst an unserem eigenen Leibe erfahren. Und da die exakte Wissenschaft es mit der Erforschung der Ausenwelt zu tun hat, so durfen wir gleich weiter sagen: es sind die Eindrucke, die wir im Leben unmittelbar durch unsere Sinnesorgane: Auge, Ohr usw. von der Ausenwelt empfangen. Wenn wir etwas sehen, horen, fuhlen, so ist das einfach eine gegebene Tatsache, an der kein Skeptiker rutteln kann.

Die Patientin L.M. von Zihl, von Crammon und Mai (1983) litt als Folge einer Durchblutungsstorung an einer seltenen Beeintrachtigung der Wahrnehmung. Sie war weitgehend blind fur Bewegungen, wahrend andere Sehleistungen wie Sehscharfe, Farbensehen, Erkennen und Lokalisation unbewegter Objekte intakt waren. Sie beschrieb ihre Wahrnehmung beim Eingiesen von Flussigkeiten in einen Behalter: Die Flussigkeiten erschienen ihr wie gefroren. Sie konnte auch die Bewegung von Personen nicht wahrnehmen. Sie war verunsichert, weil die Personen standig an anderen Stellen im Raum auftauchten. Mit dem Verlust der Bewegungswahrnehmung geht auch die Fahigkeit zur Einschatzung von Geschwindigkeiten verloren. Damit einher ging eine Verunsicherung beim Uberqueren einer Strase.

In der modernen Gastronomie werden die gewohnten Farben von Speisen radikal geandert. Die Alltagserfahrung zeigt aber, dass die Farben von Nahrungsmitteln fur die Bewertung wichtig sind. Allein die Werbeaktivitaten und Supermarktangebote zeigen, welche Rolle der Farbe zugewiesen wird. Entsprechende Untersuchungen belegen, dass die Farben einen Einfluss auf Geruch und Geschmack haben. So wurde gezeigt, dass die Erkennung eines Nahrungsmittels uber den Geschmack verschlechtert wird, wenn die Farbe kunstlich verandert wurde. Identifikationsleistungen sind besser, wenn neben dem Geschmack auch die gewohnte Farbe verwendet werden kann: das Rot der Tomate oder das Blau der Heidelbeere. Ahnliche Ergebnisse wurden auch beim Riechen erzielt. Moglicherweise liefert die Farbe eine Zusatzinformation, die »top down« auf die Identifikation von Objekten beim Riechen oder Schmecken Einfluss nimmt.

Scripts of familiar activities store the temporal order of events. This enables us to generate predictions about which event will follow another. When an event does not unfold in the chronological order, a mismatch arises between the predictions and the external sensory input which is perceived as a conflict. The detection of this mismatch is accomplished by a comparison mechanism (Zacks et al., 2007; Barsalou, 2009). We have applied pupillometry to investigate the nature of this comparison process. We further tested for individual differences in the efficiency of the mismatch detection. Participants were presented the title of an event sequence to trigger predictions about the order in which events would unfold. Subsequently, three script events were presented one at a time. The events either unfolded in the correct chronological order or included temporal violations at different points within the event triplet. Violations of the temporal order had to be detected. As soon as it was detected, the trial had to be terminated. We found that a temporal violation elicited a large pupillary response in all individuals indicating that the comparison between the predictions and the external sensory input was accomplished online and worked equally well for all individuals. However, not all individuals terminated the trial after having detected the violation. Results showed that efficient individuals who responded adequately had a greater pupillary response than inefficient individuals suggesting that they invested more cognitive resources. The results are discussed in light of theories of behavioral performance and conflict-monitoring.

Whether attention can be split between multiple regions in space simultaneously is an ongoing controversy in attention research. We argue that the debate could be resolved if the distribution of target locations over hemifields and task difficulty are both considered. This premise was tested in five experiments in which 48 subjects compared the identity of two out of four stimuli. In an easy task, within each hemifield, performance (reaction times and error rates) was better for adjacent targets than for separated ones, but across hemifields, performance for separated and adjacent stimuli was similar. In difficult tasks, performance was always better when the stimuli were presented across the hemifields indicating a bilateral field advantage. Moreover, the difference between adjacent and separate conditions within one hemifield diminished with increasing task difficulty. We propose a modified model of visuo-spatial attention, which permits the hemispheres to maintain and control simultaneous attentional foci.

The aim of the study was to identify central executive activity in the event-related potential (ERP) in the time and space domain. Lists of three to eight consonants were presented sequentially. After each list the ordered recall of the three most recent items was required. In this running memory task the updating of working memory contents from the fourth letter on may be understood as a control process. ERPs elicited from each consonant presented in the lists were subtracted from those of a control condition that was also applied to the participants. The difference waveforms showed fronto-central distributed positivities, probably indicating the activity of a postulated central executive. This finding confirms those of neuroimaging studies that localize executive activity to prefrontal brain areas.

Information processing in working memory was investigated in a paradigm with a pseudo-random sequence of visually presented consonants. The subjects' task was to memorize seven sequentially presented letters per trial and to recall the sequence (MEMORY task). Even-related potentials (ERPs) were selectively averaged for each of the seven positions of consonant presentation within a trial. The later a consonant was presented within a trial the smaller the P300 amplitude elicited by the consonant. The number of recall errors increased, however, from first to last presentation position. In a control task identical to the MEMORY condition consonant were presented. To limit the working memory load to one element, subjects had to count the number of letters within trials showing a specific physical criteria. P300 amplitude did not depend on presentation position. P300 was shown to covary with the amount of processing resources available for a task. We assume that increasing working memory load consumes processing resources that are not available for the processing of the incoming stimuli presented later in the trial.

Rather than focusing only on age-related increases in performance, I believe that it is more profitable to study the determinants of competent performance at various age levels. Providing empirical characterizations of changes in task execution as development progresses inform models of development. I make some general assumptions. First, a psychology of performance change is a learning theory. Second, learning is restructuring and reorganization of knowledge. Third, cognitive performance is a goal-related combination of procedural knowledge and conceptual knowledge. According to this view, cognitive development is a change in the way in which individuals express, recognize, and use particular forms of knowledge (Chi & Rees, 1983; Weinert & Hasselhorn, 1986). That available organized knowledge exerts a considerable influence on cognitive tasks and problems is no longer debated (Klix, 1986; Weinert & Waldmann, 1988).